Computer Network Tutorial

Introduction of Computer Network Types of Computer Network Network Topology Computer Networking Architecture Transmission Modes (Data Flow) Basic Networking Devices Integrate Services Digital Network (ISDN)


OSI Model TCP/IP Model

Physical Layer

Digital Transmission Analog Transmission Transmission Media Switching

Data Link Layer

Error detection and Error correction Data Link Control Multiple Access Aloha

Network Layer

Network Layer - Logical Address Address Mapping Unicast Routing Protocol

Transport Layer

Process to Process Delivery User Datagram Protocol Transmission Control Protocol Stream Control Transmission Protocol Session Layer and Presentation Layer

Application Layer

Domain Name System Application Protocol E-mail Cryptography


Classes of Routing Protocols Classification of Routing Algorithms Controlled Access Protocols in Computer Networks Differences between IPv4 and IPv6 Fixed and Flooding Routing Algorithms Advantages and Disadvantages of Fibre Optics Cable APIPA Difference between Active and Passive FTP Fiber Optics and its Types Method of Joining and Fusion of Fiber Optic Cable Define Framing in Computer Network Disadvantages of Computer Network Mesh Topology Diagram in Computer Network Ring Topology in Computer Network Star Topology in Computer Networks 4G Mobile Communication Technology Advantages and Disadvantages of LAN Advantages and Disadvantages of MAN Advantages and Disadvantages of WAN Application Layer in OSI Model Cyclic Redundancy Check Example Data link layer in OSI model Difference between Transport and Network Layer Hamming Code Example Network Layer in OSI Model Session Layer in OSI Model Transport Layer in OSI Model Two Port Network in Computer Networks Uses of Computer Networks What is Computer Network What is Framing in a Computer Network Advantages and Disadvantages of Bus Topology Difference between Star Topology and Bus Topology Subnetting in Computer Network Subnetting Questions and Answers What is Bus Topology What is Network Topology and Types in Computer Networks Access Control in Networking Basic Characteristics of Computer Network Benefits of SOCKS5 Proxy in Computer Networks Computer Network viva Questions Difference between BOOTP and RARP Difference Between Network Topologies and Network Protocols Difference between NFC and RFID Difference Between Point-to-Point Link and star Topology Network Differences Between MSS and MTU Differences Between Trunk Port and Access Port Different Modes of Communication in Computer Networks MIME Protocol in Computer Networks Modes of Communication in Computer Networks Network Attack in Computer Network Port Address in Networking Simplest Protocol in Computer Network Sliding Window Protocol in Computer Network Stop And Wait Protocol in Computer Networks TCP 3-Way Handshake Process in Computer Networks What is a Proxy Server What is APPN What is ICMP Protocol What is Point-to-Point Protocol What is Port Address in Networking What is the HDLC Protocol What is VRRP Protocol Difference Between Analog and Digital Signals Difference Between Hub and Repeater Difference between Repeater and Switch Difference Between Transparent Bridge and Source Routing Bridge Source Routing Bridge in Computer Networks Transparent Bridge in Computer Networks Transport Protocol in Computer Networks Types of CSMA in Computer Networks What is Wired and Wireless Networking Network Security in Computer Network Disadvantages of Extranet Difference Between TELNET and FTP Define Protocol in Computer Networks Guided Transmission Media in Computer Network What is a Gateway in a Computer Network IGMP in Computer Networks LAN Protocols in Computer Networks MAN Meaning in Computer Modulation Techniques in Computer Networks Switching in DCN TCP/IP Applications What is IGMP? What is Modem in Networking What is Non-Persistent CSMA Difference between Cell Splitting and Cell Sectoring Forouzen Computer Network Open Loop and Closed Loop Congestion Control Types of Cluster Computing WAP-Wireless Access Point What are the elements of the Transport Protocol Difference between Gateway and Switch Flow Control in Data Link Layer Body Area Network Flooding in Computer Network Token Ring in Computer Networks VoIP in Computer Networks What is Infrared Transmission Congestion Control Techniques Forward Error Correction (FEC) Switching Techniques What is Telnet in Computer Network What are the Types of IPv4 Addresses IEEE 802.6 (DQDB) IEEE 802.15.4 Technology What is HDLC (High-level Data Link Control)? What is SMS Hubbing in Telecom? Circuit Switching in Computer Networks Communication Satellites in Computer Networks Features of HTTP Protocol IMAP4 (Internet Message Access Protocol) Internet Services How to Set up a Wireless Router Internetwork Routing in Computer Networks Distributed Computing System Features of GSM The 802.11 MAC Sublayer Protocol What is IEEE 802.3? What are Hubs and Switches in Computer Networks? What is Modem in a Computer Network? What is multicasting in Computer Networks? GSM -The Mobile Station What is Network Server? Slotted Aloha in Computer Network What is Ethernet in Computer Networks What is Arpanet? Radio Access Network (RAN) TCP 3-Way Handshake Process PING SWEEP (ICMP SWEEP) Print Server Private IP Address Security Services in Computer Networks Protocol Data Unit (PDU) CSMA with Collision Avoidance (CSMA/CA) What is Gateway in Computer Network? Advantages of Networking Data Link Layer Design Issues DHCP in Computer Networks Internet Security Association and Key Management Protocol (ISAKMP) What is Switch Hub? Telnet Full form in Networking Multimedia Systems Quality of Service in Computer Networks What is Carrier Sense Multiple Access (CSMA)? What is Circuit Switching What is Duplex Network? What is Web Protocol Network LAN Technologies Classes in Computer Network Low-Density Parity Check (LDPC) Wireless Internet Service Providers(Wisps) What is Handshaking?

What is Arpanet?


The initial computer network to use packet shifting to link geographically separated computers was the ARPANET (Advanced Research Projects Agency Network), which set the stage for the eventual creation of the Internet. It was created in the late 1960s and early 1970s by the Advanced Research Projects Agency (ARPA) of the US Department of Defense to link computers and academics at different universities and research facilities. To develop a strong, dependable and decentralized communication system that could be utilized for both military and academic reasons, the United States government supported ARPANET.

What is Arpanet?

The creation of ARPANET involved the cooperation of numerous academics and organizations. Massachusetts Institute of Technology (MIT) researcher Larry Roberts introduced the network idea in 1967. Eventually, ARPA took over the project and supplied the money required to bring the network to fruition.

In 1969, the University of California, Los Angeles (UCLA) became home to the first ARPANET node. Several universities and research facilities, including the University of Utah, MIT, and Stanford Research Institute (SRI), added more nodes during the ensuing years. By 1971, the network could support 15 nodes.

Numerous innovations that are now fundamental to the current internet originated with ARPANET. For instance, the first online chat system was created on the ARPANET in 1973, and the first email message was delivered over the network in 1971. Furthermore, ARPANET initially implemented the TCP/IP protocol suite, now the industry standard for Internet communication.

History of ARPANET

The Advanced Research Projects Agency, or ARPA, a division of the US Department of Defense, launched ARPANET in 1969. Thanks to the contributions of several colleges' PCs, ARPANET was established. Technology facilitates the exchange of messages and information between computers. Playing it was primarily intended to be a long-distance diversion. People were forced to talk about their experiences. The Defense Data Network and other military networks received access to the newly updated ARPANET in 1980.

One could argue that the development of this technology was a significant step forward for other existing algorithms and concepts on the Internet. It is also regarded as the forerunner of the Internet that people use today. It was regarded as the first successful network in history and the first fully functioning and operational packet-switching system of computer networks. Additionally, it put into practice the reference TCP/IP paradigm.

Using packet-switching technology to support a wide range of research equipment was the primary goal of the ARPANET's creation. It also made it possible to exchange resources with Department of Defense contractors. The network links the research facilities, several governmental buildings and military installations. Because ARPANET worked with services like email and many more, it quickly gained popularity among all the researchers.

Characteristics of ARPANET in Computer Networks

Following are some of ARPANET's features, which will facilitate the pupils' comprehension of the network.

  • In essence, ARPANET is a Wide-Area Network (WAN). The Advanced Research Project Agency developed it in 1969.
  • ARPANET was designed to support a specific nuclear tank, which is a large object.
  • Before the development of ARPANET, every network used the circuit switching principle and had a telephone connection. However, this left the network somewhat exposed. If just one line was lost, all of the ongoing conversations would end.
  • The first technology to apply the packet switching principle was the ARPANET. Both host machines and a subnet's reach were tested.
  • In essence, this subnet was a datagram subnet. Certain minicomputers (Interface Message Processors, or IMPs) were present in every subnet.
  • Every network node had a specific link to the IMP, and a host was connected via a short cable.
  • The host could send the IMP certain messages with a maximum bit count of 8063. After splitting these communications into individual packets, the IMP would send each packet separately in the direction of the main target.
  • The ARPANET subnet essentially served as the first electronic store-and-forward packet-switching network. Thus, packets were stored correctly before being transmitted.
  • The host and subnet were the two distinct components of the ARPANET software that were later separated.
  • The TCP/IP paradigm and protocol were subsequently created in 1974. As more networks began to link to the ARPANET, this was done to manage the various communications across the internet. The development of this architecture made LAN connections to the ARPANET much simpler.
  • In 1980, there were many LAN connections made to the ARPANET, making locating the hosts more challenging and costly. Therefore, the Domain Naming System, or DNS, was created to map hostnames to IP addresses and arrange all of the machines into various domains.

Architecture of ARPANET

The ARPANET architecture aimed to create a decentralized, fault-tolerant communication system that could link every computer on the network without requiring specialized phone connections. Packet switching divides data into tiny packets and delivers each separately over the network, transferring data over the system.

The network was constructed using a hierarchical structure, with smaller nodes at the bottom and backbone nodes at the top. The backbone nodes, which were usually found in large government and research institutions, carried the bulk of network traffic and were connected to the smaller nodes, which were situated at universities and other research facilities.

The ARPANET employed a distributed routing method, which gave each node the freedom to choose the optimal route for data to travel to guarantee that the network was fault-tolerant. An Interface Message Processor (IMP), a specialized computer, was installed in every node and was in charge of data routing between nodes. Network Control Program (NCP), a protocol created especially for ARPANET, was how the IMPs interacted with one another.

Apart from distributed routing and packet switching, ARPANET developed several other important ideas that are still used today.

Some important among them are as follows:

  • Host-to-host communication: The ARPANET was the first network to provide direct computer connection rather than requiring all traffic to go via a central hub.
  • Principle of end-to-end: The ARPANET was intended to be a robust and simple system, with the majority of intelligence and complexity found at the endpoints or individual computers rather than the network it.
  • Layered protocol stack: ARPANET was the first network to employ this technique, with each layer in charge of a distinct facet of network communication.
  • TCP/IP protocol suite: The TCP/IP protocol suite was first used by the ARPANET and is still a crucial component of internet communication today.

Even though ARPANET was eventually shut down in 1990, its architectural heritage is still present in how computer networks are designed and constructed today.

Features of ARPANET

What is Arpanet?

For its time, the ARPANET was distinctive and innovative due to several important features.

The network's primary characteristics include the following:

  • Packet Switching

The first network to use packet switching in operation was the ARPANET. When packet switching is used, information is split up into tiny packets and delivered over the network individually. This communication mechanism, which shared communication links among several computers, allowed data transfer to occur more quickly and effectively.

Most communication networks employed circuit switching before packet switching, which necessitated the establishment of a dedicated communication line between two devices. Packet switching transformed communication networks and cleared the path for a world powered by the internet.

  • Decentralized Network Architecture

Because of its decentralized network architecture, every computer connected to the ARPANET could communicate with several other computers. This allowed information to be routed around damaged or crowded locations and strengthened the network's resilience to breakdowns. Routers were used to direct data packets to their destinations, enabling the ARPANET's decentralized architecture. Because the ARPANET's routers were built to be intelligent and flexible, the network could manage various traffic situations.

Decentralized networks are utilized for many things, such as distributed software, file sharing, and Bitcoin transactions. Furthermore, the consensus-maintaining function of blockchain technology depends on a decentralized ledger to record transactions. Because decentralized networks have the potential to offer higher levels of security, privacy, and autonomy than centralized networks, they have become more and more popular in recent years.

  • Resource Sharing

One of ARPANET's main goals was to enable academics to exchange resources like computer programs, data sets, and processing power. This was accomplished by creating protocols that let users access remote resources like local resources. One such protocol was Remote Job Entry (RJE), which lets users send jobs to computers at a distance and get the results back over the network.

Resource sharing is still a crucial component of networks and the Internet today, with various technologies and protocols used to share computing resources, such as cloud computing, virtualization, and distributed computing systems.

  • Email

The first network to facilitate email communication was the ARPANET. Ray Tomlinson, a computer expert working on the network then, sent the first email message in 1971. One of the most widely used applications of ARPANET was email communication, which enabled researchers to communicate more effectively than ever. The email protocols created for the ARPANET made modern email systems possible.

In addition to email, ARPANET contributed to developing new firewalls and other network security technologies still in use today to guard against cyberattacks and unauthorized network access.

  • File Transfer

In addition, file transfer protocols offered by ARPANET enabled users to upload and download files from distant places. Users may send files across distant computers via the ARPANET using the File Transfer Protocol (FTP) created for the network. FTP swiftly became one of ARPANET's most widely used applications, facilitating data sharing and improving academic teamwork.

  • Remote Login

Through the ARPANET, users can access and operate distant computers like local computers. The creation of remote login technologies like Telnet made this possible. It made it possible for users to easily access and operates distant PCs. This was a major breakthrough for academics that needed to access sophisticated computers and resources in remote regions. Ultimately, it sparked the creation of cloud computing and virtual private networks (VPNs), two technologies for remote access.

  • Error Correction

One essential component of the ARPANET was error correction, ensuring that data sent over the network was received accurately and without errors. Using an approach called Automatic Repeat request (ARQ), errors could be found and fixed at the data connection layer of the network protocol on the ARPANET.

Data was divided into packets for transmission across the network, and each packet had a header with the destination address and the sequence number, among other details. A checksum created based on each packet's contents was used to verify that it contained no mistakes once the packets arrived at their destination. The sender would retransmit the packet until it was successfully received. If an error is found, the receiving node will request it be sent again.

This error-correcting mechanism was essential to guarantee precise and dependable data transmission across the network. Error correction is necessary to prevent data loss or corruption during network transmission, which could result in inaccurate or deleted data.

Error correction is still a crucial component of network protocols today. More sophisticated error correction methods have been created to guarantee the dependable transfer of data over high-speed networks. Among these methods are Automatic Repeat reQuest with Selective Repeat (ARQ-SR), which allows the recipient to request retransmission of only the packets that were received with errors, rather than the entire packet stream, and Forward Error Correction (FEC), which adds redundant data to transmitted packets to enable the receiver to detect and correct errors.

  • Research and Innovation

The ARPANET research project aimed to expand the realm of computer networking capabilities. This culture of innovation and experimentation made possible the creation of technology we now take for granted, such as the Internet of Things, cybersecurity, telemedicine, e-commerce, social media, online collaboration tools, etc.

Importance of ARPANET

In many respects, ARPANET was significant for a variety of industries because it promoted worldwide invention, teamwork, and communication. It has had a significant global impact and continues influencing how we work and live in the modern world. Let's examine the significance of ARPANET in several industries.

  • Science and Research

Collaboration and data sharing among scientists and academics made possible by ARPANET resulted in important breakthroughs across various disciplines. For example, scientists worked together on human genome research projects in the 1970s by exchanging data over the ARPANET. The first automated DNA sequencing machine was created due to this partnership, opening the door for contemporary genetic research.

Furthermore, in the 1970s, ARPANET was utilized to link geographically dispersed laboratories, constructing the largest particle accelerator, the Large Hadron Collider (LHC). Thousands of scientists and engineers from more than 100 nations worked on the LHC project, sharing data and collaborating over ARPANET.

  • Education

ARPANET significantly advanced education by providing remote access to resources like supercomputers, databases, and other scientific instruments. For instance, in the 1980s, researchers at the University of California, Berkeley, conducted tests and simulations that would not have been feasible without the ARPANET by using it to remotely access a supercomputer at the "Lawrence Livermore National Laboratory."

  • Business and Commerce

ARPANET had a huge impact on business by facilitating remote access to resources, data sharing, research, and collaboration between organizations and their partners in diverse locations. In the 1980s, IBM developed a remote ordering system for customers using ARPANET. Customers could place orders for IBM items using this system from any location with an ARPANET connection.

"American Airlines" also developed a reservation system using ARPANET in the 1980s that let users book flights from far-off places. The online booking systems used today by airlines and other travel-related firms were modeled after this one.

  • Government

Because ARPANET made it possible for resources to be accessed remotely and made it easier for departments and agencies to communicate with one another, its effects on government could be measured. In the 1980s, for example, the U.S. Department of Defense created a method to exchange satellite data between several military branches using ARPANET. Thanks to this technology, the military was able to organize and react to threats more skillfully.

  • Social Life

ARPANET revolutionized social life by facilitating communication between individuals in different locations and time zones. Modern online gaming was pioneered in the 1970s when a group of computer enthusiasts created the multi-user game "Maze War," which allowed users to connect to ARPANET from different locations and play together in a virtual environment.

  • Healthcare

By facilitating remote access to medical resources and data sharing and collaboration between physicians and researchers, ARPANET substantially impacted healthcare. Physicians at the University of Pittsburgh were able to remotely view medical records and photos from a Maryland hospital in the 1970s thanks to ARPANET. Significant improvements in patient care and medical research resulted from this collaboration.

  • Defence

ARPANET was crucial in the defense industry because it facilitated secure communication and cooperation between many military departments and agencies. Thanks to ARPANET, the U.S. military created a secure message system known as "E-mail" in the 1970s, which allowed agencies to exchange confidential information.

Advantages of ARPANET

  • ARPANET was built to function even in the event of a nuclear assault
  • Email collaborations were conducted with it.
  • It led to a breakthrough in the defence sector's crucial file and data transfer.

Limitations of ARPANET

  • Managing an increased number of LAN connections proved challenging.
  • It was unable to keep up with technological advancements.


The ARPANET established the groundwork for a global network, and its impact continues to propel the advancement of technologies that allow us to have greater connectivity than previously. Its features such as fundamental technologies packet switching, TCP/IP, email, and remote access have made it possible for people to collaborate and communicate in real-time, send and store data securely, access information remotely, and mobile. They have also created an environment that is conducive to innovation.

The development of new technologies like 5G, edge computing, IoT, and AI, which will further connect people, devices, and systems, will continue to be fueled by these ARPANET components. Our world will become more interconnected, enabling people, groups, and communities to collaborate effectively and easily, greatly enhancing our quality of life.